SMITH, PAUL W., WALTER J. HENDRICKSON, and RONALD J. WOODS
IHS Energy Group, Oklahoma City, OK

Abstract: Significance of Accurate Carbonate Reservoir Definition and Delineation

Reservoir definition is often vague or poor even in mature areas due to mis-identified angular unconformities, facies changes, or poor understanding of the relationships existing in deep portions of a basin that were undrilled until late in the development history. Typically there does not exist any mechanism to correct misnamed reservoirs as it is often dismissed as being "purely academic", insignificant, or unnecessary. As a result of a recent Gas Research Institute project (GRI-96/0196), a classic example of the significance of accurate reservoir definition and delineation was identified. 1,232 well completions had been reported as being from the Chester (Mississippian), when, after detailed correlations, it was demonstrated that only 221 completions could be attributed to the Chester within the study area. Consequently, the ultimate recovery of the Chester diminished from 1,781 BCF to 277 BCF gas. Most of the gas was being produced from carbonate reservoirs belonging to the above lying Springer Group and could be identified as such through regional stratigraphic correlations. Although found at comparable depths, the carbonate reservoirs belonging to the Springer Group typically produce 50 to 80 percent more gas per completion than completions within the Chester.

This paper will present the findings which explain the significance of the disparity between the often misidentified reservoirs. These finding demonstrate that opportunities exist for significant infield development, trend extensions, and the further development of newly recognizable trends. Basinwide stratigraphic correlations and detailed geologic analysis will be presented.

AAPG Search and Discovery Article #90921©1999 AAPG Mid-Continent Section Meeting, Wichita, Kansas